1. Field of the Invention
The present invention relates to a scanning laser microscope.
2. Description of the Related Art
Scanning laser microscopes are capable of optically slicing samples such as living cells and tissues without damaging the samples, and obtaining a plurality of two-dimensional tomogram images to obtain three-dimensional images from the plurality of two-dimensional tomogram images.
In the scanning laser microscope which observes a living sample, a fluorescent reagent or fluorescent protein introduced into the sample is irradiated with laser light, and fluorescence is measured from the sample and formed into an image. In this case, when a plurality of types of fluorescent reagents or fluorescent proteins are introduced into the sample, it is possible to observe a plurality of chemical substances in the cell. To excite these types of fluorescent substances, excitation laser light having a plurality of wavelengths is necessary.
On the other hand, a color degradation phenomenon occurs in which a fluorescent amount from the fluorescent substance decreases with elapse of an irradiation time of the excitation light. To solve the problem, a method has heretofore been proposed in which unnecessary excitation light is interrupted to prevent the color degradation as much as possible in the scanning laser microscope.
For example, in an optical path, a shutter or an optical filter is mechanically inserted, or an acoustooptic device (AOTF, AOD, AOM, etc.) described in a document (AKIS P. GOUTZOULIS and DENNIS R. PAPE, DESIGN AND FABRICATION OF ACOUSTO-OPTIC DEVICES, Marcel Dekker, Inc., 1994, pp. 246-259) and shown in FIG. 9, EOM or the like is inserted. Accordingly, in accordance with an irradiation position, an intensity of laser light is adjusted, and the wavelength is selected in a set procedure, and the laser light having a desired wavelength and intensity can be applied only to a desired portion. As shown in FIG. 9, the acoustooptic device is capable of producing sound waves therein by an electric signal from the outside to make a refractive index change in the device. The refractive index change makes it possible that transmittance of incident light is controlled.
When data is obtained in a time series by use of a plurality of laser wavelengths, a plurality of modulating sections need to be used in performing the control. However, in this case, when a plurality of modulating sections are driven with a single synchronous signal, a difference is made in a response time from when the electric signal is supplied to the acoustooptic device until the function (change of the refractive index) is developed, that is, a delay time by a difference of the type of the acoustooptic device. As a result, as shown in FIG. 10, an actual laser irradiation position 82 shifts from a laser irradiation position 81 to be irradiated by a user in each modulating section.